(i) Field of the Invention
The present invention relates to new nucleic acid sequences, particularly DNA sequences, encoding insecticidal proteins produced by Bacillus thuringiensis strains. Particularly, new nucleic acid sequences, particularly DNA sequences encoding proteins designated as Cry2Ae, Cry2Af and Cry2Ag are provided which are useful to protect plants from insect damage. Also included herein are micro-organisms and plants transformed with a nucleic acid sequence, particularly a DNA sequence, encoding at least one of the newly isolated Cry2A proteins.
(ii) Description of Related Art
Bacillus thuringiensis (abbreviated herein as “Bt”) is well known for its specific toxicity to insect pests, and has been used since almost a century to control insect pests of plants. In more recent years, transgenic plants expressing Bt proteins were made which were found to successfully control insect damage on plants (e.g., Vaeck at al., 1987, Jansens et al., 1997).
Despite the isolation of quite a number of insecticidal Bt genes, the search for new genes encoding insecticidal proteins continues. Indeed, insecticidal Bt proteins are known to have a relatively narrow target insect range compared to chemical insecticides. Also, having multiple toxins to the same target insect species allows the use of proteins having different modes of action so that insect resistance development can be prevented or delayed. And, insecticidal Bt proteins with different amino acid sequences have different levels of insecticidal efficacy against specific insects, making it desirable to have several different insecticidal proteins available in order to be able to control the relevant insect pests of different crop plants.
Previously, several types of Cry2A-proteins were identified (see Crickmore et al., 1998, incorporated herein by reference).
The new Cry2Ae protein of this invention has the highest amino acid sequence identity to the Cry2Aa1 protein (Donovan et al., GenBank accession number M31738), but still differs in about 9 percent of its amino acid sequence.
The closest sequence identity to the Cry2Af protein was found in the Cry2Ab1 protein (Widner and Whiteley, GenBank accession number M23724), but both proteins still differ in about 5 percent of their amino acid sequence.
The closest sequence identity to the Cry2Ag protein was found in the Cry2Ac1 protein (Wu et al., GenBank accession number X57252), but both proteins still differ in about 20 percent of their amino acid sequence.
Further known Cry2A proteins include the Cry2Ad1 protein (Choi et al., 1999), and other Cry2Aa, Cry2Ab, and Cry2Ac proteins (Crickmore et al., 1998). Cry2A-like proteins and DNA sequences encoding them are also shown in U.S. Pat. No. 5,338,544, in published PCT patent application WO 00/26371 and in published PCT patent application WO 98/40490.
Expression of Cry2A-type proteins in plants has been described, e.g., in Kota et al. (1999) and in published PCT patent application WO 00/26371.